This is a sequel to Bitter Seeds, part two of the alternative history Milkweed trilogy. Be advised: this is one continuous story told in 3 chunks, not a linked set of stand-alones, so it really is best to start at the beginning.

The Soviet Union may have won World War II, thanks in no small part to the contributions of German technomages, but
Britain
has remained unconquered. Now, however, the wizards who guarded
England
from invasion and subversion, through the years of fighting and through the decades of Cold War, are dying.

England
’s defenses are crumbling.

Not only does that mean that dangers can penetrate from outside, other threats, internal ones, are no longer checked: spiritual dangers like fear, desperation, and despair; but also hidden threats, like Junkman, an imbedded agent forgotten even by his own fatherland. Once he realizes that the Watchmen are losing ground  by becoming part of it  he perceives an opportunity to strike.

And then there are ambiguous hazards, like the renegade twins who cross the Iron Curtain, which no one should be able to do.

Raybould Marsh, the last, best hope of Milkwood, doesn’t consider himself fit for the task of saving England’s tenuous freedom, and as he witnesses the erosion of all that is worth fighting for, living for, or dying for, he has to find overlooked sources of strength and unlikely allies.

If parts of the book seem almost unbearably grim, stick with it. There’s great character development, not to mention descriptions of nuclear physics as comprehended by magic-users, and there’s a wonderful payoff, one which makes perfect sense yet still comes as a surprise, and which sets up the next book with an “And now for something completely different!” flourish. ~~ Chris R. Paige